Rotary piston compressors with liquid injection

ABSTRACT

A rotary piston compressor having a casing with two intersecting parallel cylindrical bores in which a main rotor and a gate rotor cooperating therewith are mounted to rotate. Each rotor has a hub with a substantially constant radius hub portion and with a tooth extending radially from said portion and with a recess for passage of the tooth of the cooperating rotor. The casing provides end walls for the bores with axial inlet and outlet ports for the working fluid. Injection nozzles or fine openings for liquid serving as sealant and for cooling the working fluid are provided in the end walls of the gate rotor bores in such position, that they are covered by the constant radius portion of the gate rotor hub at the beginning of the compression cycle and are uncovered in the recess of said hub towards the end of the compression cycle.

United States Patent [191 Emanuelsson et a1.

[11] 3,790,315 Feb. 5, 1974 ROTARY PISTON coMPREssoRs wITII LIQUID INJECTION Inventors: Kaj Bengt Ingemar Emanuelsson, Wilrijk, Belgium; Bo Olof Roland Arnegard, Skarholmen, Sweden Atlas Copco Aktiebolag, Nacka, Sweden Filed: Sept. 28, 19'i1 App]. No.: 184,520

[73] Assignee:

[30] Foreign Application Priority Data Oct. 1,1970 Sweden ..13310/70 [56] References Cited 7 UNITED STATES PATENTS 1'0/1970 Brown 418/114 10/1971 Borisoglebsky et a1 418/190 X 7 Primary Examiner-Carlton R. Croyle Assistant Examiner-Michael Koczo, Jr. Attorney, Agent, or Firm-Eric Y. Munson ABSTRACT A rotary piston compressor having a casing with two intersecting parallel cylindrical bores in which a main rotor and a gate rotor cooperating therewith are mounted to rotate. Each rotor has a hub with a substantially constant radius hub portion and with a tooth extending radially from said portion and with a recess for passage of the tooth of the cooperating rotor. The casing provides end walls for the bores with axial inlet and outlet ports for the working fluid. Injection nozzles or fine openings for liquid serving as sealant and for cooling the working fluid are provided in the end walls of the gate rotor bores in such position, that they are covered by the constant radius portion of the gate rotor hub at the beginning of the compression cycle and are uncovered in the recess of said hub towards the end of the compression cycle.

4 Claims, 2 Drawing Figures PAIENTEDFEB 51914 I 3.190.315

SWEEI 1 0F 2 KAJ BEN-GT INGET-IAR ET-IANUELSSON and B0 OLOF ROLAND ARNEGARI) BY HUNSON & FIDDLER,

Attorney 5 PAIENIEB H5 5 5 SHEET 2 BF 2 I RAJ BIJNGT INGEMZXR EF'lANU ELSSON and B0 OLOF ROLAND ARNEGARD INVHNI'ORS BY MUHSON & FIDDLER,

Attorneys.

I ROTARY PISTON COMPRESSORS WITH LIQUID INJECTION SUMMARY OF THE INVENTION This invention relates to a rotary piston compressor having a main rotor and a gate rotor provided each per se with a hub having a hubportion with substantially constant radius and with a tooth extending radially from said hub portion, said hub on the main rotor having a recess adjacent the main rotor tooth for the passage of the gate rotor tooth, said hub on the gate rotor having a recess adjacent the gate rotor tooth for the passage of the main rotor tooth, and said compressor having a casing with intersecting cylindrical bores, one for each rotor, said rotors being mounted for rotation in said casing and arranged to sealingly cooperate one with the other and with the casing for transportation of limited volumes of a working fluid through the compressor under simultaneous reduction of the size of said volumes, and said machine having axial inlet and outlet ports for the working fluid and means for synchronizing the rotation of the rotors.

One object of the invention is to provide means for liquid injection in compressors of this type which are of simple construction and such design that the injected liquid effectively serves to seal the leakage through the clearances in the compressor and furthermore coolsthe working fluid during the compression cycle. A further object of the invention is to cool the working fluid in the portions of the compressor where the greatest heat generation occurs. A still further object of the invention is to increase the efficiency of the compressor and to make possible compression to a high pressure BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings one embodiment of a rotary piston compressor according to the invention is illustrated by way of example. However, the invention is not limited to compressors of the described design but may be applied to modified designs also within the scope of the claims.

In the drawings FIG. 1 is a section through a rotary piston compressors on a plane through the two axes of the compressor. FIG. 2 a transverse section of the compressor on lines ll-II in FIG. 1'.

DESCRIPTION OF A SPECIFIC EMBODIMENT The rotary piston compressor illustrated in FIGS. 1 and 2 is a one or single stage toothed compressor provided with a main rotor and a gate rotor each provided with a single tooth. The compressor casing of the machine consists of a central portion 1 and two end wall pro tions 2, 3 which are bolted together with the central portion 1 by means of bolts 4. Two cylindrical bores 5, 6 with parallel axes are formed in the portion 1 which bores partially intersect. The bores 5, 6 form working chambers for a main rotor 7 and a gate rotor 8 which rotors are secured on parallel shafts 9 and 10, respectively, preferably secured by shrinking or pressure fitting or they may be made integral with the shafts. The shafts 9 and 10 are mounted in bearings 11a and 11b, respectively, fitted in the wall portions 2, ,3. The bearings 11a are cylindrical roller bearings which permit axial displacement of the shafts whereas the bearings 1117 are angle contact ball bearings which fix the shafts with respect to the position where the bearings 11b are fixed. The rotors are synchronized by means of a toothed gear transmission 12 and sealed against the working chambers in the central portion 1 of the compressor casing by sealing rings. 13, which form seals with bushings 13a which preferably may be press fitted on the shafts 9 and 10, respectively. The bushings 13a also function as spacer sleeves. The compressor casing is provided with an inlet pipe socket 14 which is formed partly in the central portion l'and partly in the end wall portions 2 and 3, and, furthermore, with an outlet pipe socket 15 formed in the end wall portions 2, 3. The inlet pipe socket 14 forms a passage 18 to inlet ports leading to the working chamber of the machine which inlet ports comprise a radial inlet port portion 19 and two axial inlet port portions 20 one in each end wall portion 2 and 3, respectivelyQThe outlet pipe socket 15 is connected to outlet ports 22 by means of outlet passages 21 one in each end wall portion 2 and 3, respectively. The central portion 1 of the compressor casing is at one side of a plane 10a through the rotor axes provided with a cooling jacket 16 which together with the cylinder wall 17 forms the cooling passage 23 for cooling liquid, such as cooling 'oil, which is preferably supplied through an inlet opening 24 and expelled through an outlet opening 25 at the under side and the upper side, respectively, of the compressor casing. The end wall portions 2, 3 are provided with passages 26 and 27, respectively, which constitute drain passages to the outside of the compressor for working fluid which may leak fluid from the working chambers in the central portion 1 of the compressor over the seals 13 and 13a. Bythe arrangement of the cooling passages 23 efficient cooling is obtained of the hottest portion of the compressor casing, i.e. the portion where most of the heat energy is generated, and it is thereby prevented that heat stresses occur in the casing and that the casing is subjected to distortion or becomes skew. The wall thickness may consequently be reduced and the casing as a whole may be designed lighter which also promotes more efficient cooling. When very efficient internal cooling by injection of cooling liquid, such as oil or water with or without a lubricating additive, then the cooling means 16, 23 may sometimes be replaced by air cooling means. I

In order to make the assembly of the compressor casing easier, guide pins 28 are provided in the central portion 1 which guide pins fit in carefully machined holes 29 in the end wall portions 2, 3. Two or three such holes may be provided at suitable positions around the bores 5, 6. The end wall portion 2 is provided with a flange 30 arranged for securing the compressor to a suitable driving motor which drives the compressor over a toothed gear 31 which is secured on the rotor shaft 9 by means of a pressure disk 32 and bolts 33 and a pair of conic'al spanner rings 34. The outer races of the angle contact ball bearings 1112 are secured in sleeve portions 35 which are formedin the 3 end wall portions 3 and which are made elastic by the provision of radial slots 36 which also serve as oil drainage passages and extend along a portion of the periphery of the sleeve portion 35. The sleeve portions 35 are also provided with axial slots 37 which are bridged by spanner bolts 38 serving to secure the outer races of the bearings 1 lb. 39 indicate oil throwing rings which also serve as puller rings for the bearings 11b. 40 indicate drain passages. 41 is a pressure disk and 42 bolts for securing the synchronizing gears 12 to the shafts in adjusted positions by means ofpairs of conical spanner rings 34. 43 is a cover for the synchronizing transmission which is secured by a spanner 44 and which is sealed against the end wall portion 3 by means of a sealing ring 45 so that oil is prevented from leaking from the transmission housing.

According to the invention the compressor is provided with means for the injection of cooling liquid in the clearances between the end walls and the hub portion with substantially constant radius of the gate rotor and through the recess in the gate rotor hub, respectively. Furthermore injection may also take place according to the demand in other parts of the working chambers of the compressor. The cooling liquid may, for instance, be oil or water, which for the purpose of internal cooling of the compressor takes up the major portion of the heat generated by compression from the working fluid. The quantity and temperature of the cooling liquid must, of course, have a certain relation to the quantity and pressure of the working fluid and the physical properties of said fluid, which every heat technician can easily calculate. The cooling liquid also serves to seal the clearances of the compressor, and, if it has lubricating properties, it may also help to lubricate the compressor. 1

By injection of cooling'liquid in the clearances between the hub portion of the gate rotor and the end walls 2, 3 the most sensitive parts of the compressor are protected and simultaneously an advantageous distribution of the injected cooling liquid is obtained.

Cooling liquid may also be injected in well known manner through nozzles 46 with openings 47 directed towards the working chamber of the main rotor. A further means for injecting cooling liquid may comprise a number of fine nozzles or holes 48 in the end walls 2, 3 of the working chamber of the main rotor tooth 49, so arranged that they are never covered by the hub portion 50 with substantially constant radius of the main rotor. Said means may preferably be disposed in the portion of the working chamber of the main rotor adjacent the outlet port 22.

According to the invention it is, however, most important that injection nozzles or holes are arranged in the end walls 2, 3 as indicated at 51, which are so disposed that they are covered during a portion of a gate rotor revolution by the gate rotor hub portion with substantially constant radius which is in the beginning of the compression cycle but are uncovered in the hub recess 53 during a later portion of the gate rotor revolution towards the end of the compression cycle. In this way a preferable axial sealing effect is obtained between the gate rotor hub and the end walls during a great part of the gate rotor revolution when the pressure drop over the clearance is large and an efficient cooling is obtained during the last part of the compression cycle when the pressure drop is smaller.

The nozzles 51 are arranged in the half of the working chamber of the gate r'otor which is adjacent the outlet opening 22.

A further cooling liquid injection means may comprise nozzles or holes 57, 58 in the peripheral walls of the bores 5, 6. The holes 57, 58 may lead from the cooling medium jacket 23 or from separate not illustrated conduits for injections of cooling liquid.

All cooling liquid nozzles or openings may be fed from a non illustrated pump in a manner well known in oil injected compressors an'dthe cooling liquid may be separated from the working fluid in a separator provided after the compressor in known manner. The separated cooling liquid may be cooled for renewed use in the compressor. Cooling liquid injected according to the invention in the gate rotor end wall clearances may be helpful to keep the rotor in correct axial position between the end walls 2, 3. The illustrated compressor has a compression clearance space which gradually goes down to Zero and, in order to avoid liquid shocks in the compressor at the end of the compression cycle, it may sometimes be preferred to chamfer or round off a portion 55 of the concave gate rotor tooth flank near the base of the tooth, which has been illustrated very exaggerated in FIG. 2 atthe leading flank 56 of the gate rotor tooth 54. Passages in the gate rotor ends or the end walls 2, 3 may also serve to drain out small trapped gas and/or liquid quantities to the inlet port for avoiding liquid or working fluid shocks.

The toothed compressor above described should only be considered as an example and may be modified in different ways within the scope of the claims.

We claim:

l. A rotary piston compressor with liquid injection comprising a main rotor and a gate rotor provided each per se with a hub having a hub portion with substantially constant radius and with a tooth extending radially from said hub portion, said hub of the main rotor having a recess adjacent the main rotor tooth for the passage of the gate rotor tooth, said hub of the gate rotor having a recess adjacent the gate rotor tooth for the passage of the main rotor tooth, and said compressor having a casing with intersecting cylindrical bores, one for each rotor, and end walls bounding said bores axially, said rotors being mounted for rotation in said casing and arranged to sealingly cooperate one with the other and with the casing for transportation of limited volumes of a working fluid through the compressor under simultaneous reduction of the size of said volumes, and axial inlet and outlet ports in said end walls for the working fluid and means in said compressor for synchronizing the rotation of the rotors, said compressor being characterized by the provision of injection nozzles for cooling liquid in a portion of said end walls of the gate rotor bores, which during the beginning of the compression cycle is covered by said constant radius hub portion of the gate rotor and towards the end of the compression cycle is uncovered in the recess of said gate rotor hub, said substantially constant radius hub portion of the gate rotor having materially larger radius than said substantially constant radius hub portion of the main rotor. I

2. A rotary piston compressor according to claim 1, in which the liquid injection nozzles in the end wall of the gate rotor bore are situated in the half of the end wall containing the outlet port.

- 3,790,315 V 6 3. A rotary piston compressor according to claim 1, 4. A rotary piston compressor according to claim 1, in which the gate rotor tooth has a leading flank which in which passages are provided in the end walls of the is chamfered over a portion near the root of the tooth gate rotor bore for the escape of trapped fluid volumes. for the escape of trapped fluid volumes. 

1. A rotary piston compressor with liquid injection comprising a main rotor and a gate rotor provided each per se with a hub having a hub portion with substantially constant radius and with a tooth extending radially from said hub portion, said hub of the main rotor having a recess adjacent the main rotor tooth for the passage of the gate rotor tooth, said hub of the gate rotor having a recess adjacent the gate rotor tooth for the passage of the main rotor tooth, and said compressor having a casing with intersecting cylindrical bores, one for each rotor, and end walls bounding said bores axially, said rotors being mounted for rotation in said casing and arranged to sealingly cooperate one with the other and with the casing for transportation of limited volumes of a working fluid through the compressor under simultaneous reduction of the size of said volumes, and axial inlet and outlet ports in said end walls for the working fluid and means in said compressor for synchronizing the rotation of the rotors, said compressor being characterized by the provision of injection nozzles for cooling liquid in a portion of said end walls of the gate rotor bores, which during the beginning of the compression cycle is covered by said constant radius hub portion of the gate rotor and towards the end of the compression cycle is uncovered in the recess of said gate rotor hub, said substantially constant radius hub portion of the gate rotor having materially larger radius than said substantially constant radius hub portion of the main rotor.
 2. A rotary piston compressor according to claim 1, in which the liquid injection nozzles in the end wall of the gate rotor bore are situated in the half of the end wall containing the outlet port.
 3. A rotary piston compressor according to claim 1, in which the gate rotor tooth has a leading flank which is chamfered over a portion near the root of the tooth for the escape of trapped fluid volumes.
 4. A rotary piston compressor according to claim 1, in which passages are provided in the end walls of the gate rotor bore for the escape of trapped fluid volumes. 